1. Field of the Invention
The present invention relates to a powder filling apparatus and a powder filling method for packing fine powder such as toner used in the developing device of an imaging apparatus such as an electrostatic copying machine or a printer, into a filling container, and a process cartridge packed with the powder by the powder filling method.
2. Description of the Related Art
Conventionally, fine powder such as toner is packed into a container to be filled with a powder with a screw feeder or an auger packer, by being let fall by its own gravity or by a pneumatic carrying device. For instance, Japanese Patent Application Laid-Open No. 2002-293301 describes an example of a pneumatic method of carrying powder.
Japanese Patent Application Laid-Open No. 2002-293301 discusses a configuration by which gas is led into powder stored in a powder feeding device to increase the fluidity of the powder and the powder is packed into a container to be filled by utilizing the pressure of the led-in gas. According to Japanese Patent Application Laid-Open No. 2002-293301, the powder in the powder feeding device is conveyed to a carrying tube by the pressure of leading-in, fed to the container to be filled via the carrying tube and, after the desired packed quantity is reached, the carriage of the powder is stopped by releasing the pressure in the powder feeding device.
However, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2002-293301, as the powder stored in the powder feeding device is packed into the container to be filed after its fluidity is enhanced with the gas, the powder is fluidized more than required, making it difficult to pack the powder into the container to be filled in high density. The more than required fluidization also causes the filling to take a longer time than otherwise.
Another filling method by which powder is carried with gas without increasing the fluidity of the powder is proposed in Japanese Patent Publication No. H06-062121.
According to Japanese Patent Publication No. H06-062121, first a fixed quantity of powder is filled into a measuring chamber by the pressure in the measuring chamber being reduced, and pressure is applied from the upstream side of the measuring chamber in the powder carrying direction to load the powder with that pressure of application.
However, in the configuration discussed in Japanese Patent Publication No. H06-062121, as the filled quantity of powder is determined by the size of the measuring chamber, if filling is to be done into the same apparatus more than once in different quantities for instance, the measuring chamber itself will have to be replaced, entailing a heavy burden. Or if a large quantity of powder is to be filled, this configuration is susceptible to clogging of the filter with the filled powder at the stage of filling the measuring chamber under reduced pressure, making it difficult to load the prescribed quantity.
Also, Japanese Patent Application Laid-Open No. H03-226402 and Japanese Patent Publication No. H07-100481 describe configurations in which powder is filled into a filling container after being increased in density by being cleared of gas it contains.
Thus, according to Japanese Patent Application Laid-Open No. H03-226402, a hollow cylindrical container having an inner chamber and an outer chamber is filled with powder, followed by deaeration of the powder through a hole inner diameter in the inner chamber, and the powder, after being compacted, is filled into a flexible container to be filled underneath.
Further, Japanese Patent Publication No. H07-100481 discusses a configuration in which powder is filled by using a horizontal auger screw into a powder filling chamber having a similar filtering function, and deaeration is performed at the same time to load the powder in high density, followed by filling of the powder into a container to be filled.
Further, the following techniques are also made known as methods of filling powder into a container to be filled in high density.
Japanese Patent Application Laid-Open No. 2002-337801 describes a method by which air is gradually driven away upward from the bottom of a filling container while avoiding scattering of the powder by filling the powder in a state in which the filling nozzle of a powder filling apparatus is surrounded by the powder within the filling container. This method is claimed to be particularly effective for thin and narrow filling containers.
Also, Japanese Patent Application Laid-Open No. H08-198203 discusses a method by which powder is filled into a container to be filled in high density and at high speed by filling the powder while raising the air suction pipe of a powder filling apparatus from a state in which the pipe is inserted into the container in advance along with the progress of the filling of the powder and thereby sucking the gas contained in the powder.